1. Field of the Invention
The present invention relates to an allocation of recorded data in an information recording medium, and more particularly to a system for recording by means of generally available recording and playback drives.
2. Description of the Related Art
As an example of an information recording system according to the related art, an optical recording and playback system for an information recording medium having target information (such as an advertisement) will be described by referring to FIGS. 3 and 9.
FIG. 3 shows a block diagram of the optical recording and playback apparatus according to the prior art. A laser light source 25 which forms a part of an optical head 2 emits light (with a wavelength of about 660 nm in the case of a DVD-RAM). The light passes through a collimator lens 24 by which the light is collimated into substantially parallel beams of light 22. The light beams 22 are irradiated onto an optical disc 11 via an objective lens 23, thereby forming a spot 21. Thereafter, the light beams are guided to a servo detector 26 and a signal detector 27 via a beam splitter 28 and a hologram element 29, for example. Signals from the individual detectors are processed by addition or subtraction to provide servo signals such as a tracking error signal and a focus error signal, which are input to a servo circuit. Based on these tracking error signal and focus error signal, the servo circuit controls the position of a drive means 31 for the objective lens 23 and that of the optical head 2 as a whole, such that the light spot 21 is positioned at a desired recording or playback area. An addition signal from the detector 27 is input to a signal playback block 41. The input signal is digitally processed after filtering and frequency-equalize processing by a signal processing circuit. A digital signal after the digital processing is processed by an address detection circuit and a demodulation circuit. Based on an address signal detected by the address detection circuit, a microprocessor computes the position of the light spot 21 on the optical disc 11, and positions the optical head 2 and thus the light spot 21 at a desired recording unit area (sector) by controlling an automatic position control means.
When an higher-order apparatus instructs the optical recording and playback apparatus to record, the microprocessor receives recording data from the higher-order apparatus and stores it in a memory, while controlling the automatic position control means to position the light spot 21 at a desired recording area. After confirming that the light spot 21 has been correctly positioned at the recording area based on the address signal from the signal playback block 41, the microprocessor controls a laser driver, for example, to record the data stored in the memory in the desired recording area.
The address signal is assigned to each information recording unit area, as shown in FIG. 6. Since the address signal is placed at the head of the recording unit area, the position of the light spot immediately before recording can be verified by detecting the address signal.
FIG. 9 shows an example of the flow of operation of an optical recording system for driving a DVD-RAM disc, as an example of the above-described optical recording system. The DVD-RAM disc is a rewritable disc defined by the international standard ISO/IEC-16824, for example.
When a disc is inserted or the optical recording system is turned on, the optical recording system first performs a processing to determine the type of the medium. In addition to the DVD-RAM, the system is usually equipped with playback functions for read-only media such as CD-ROMs or DVD-ROMs. Thus, the optical recording system initially determines the type of the medium to identify which of the above-mentioned media the inserted medium is. The manner in which the determination processing is performed differs from one system to another. For example, there is a system in which the type of the medium is determined based on the reflectivity or the analog characteristics of playback signals such as the focus error signal. In another system, the type of the medium is determined by playing back the medium's physical information retaining area provided on a disc substrate and looking at its contents (data).
Once the optical recording system identifies that the medium is of the re writable type, i.e., a DVD-RAM, it examines the recorded contents including a defect management information area to see if the optical disc has been physically formatted. If not physically formatted, the system waits until an instruction for physical formatting is issued from the higher-order apparatus or user.
When the optical disc is physically formatted, the optical recording system performs recording preparation processes such as a calibration processing and logical consistency verification, and then waits for instructions from the user or higher-order apparatus. Upon receipt of some kind of a command, the optical recording system checks the type of the command and, when it is a record command, performs a record processing. When the command is instructing a playback, formatting, or disc retrieval, for example, the system performs a relevant processing. Normally these processes come to an end without a hitch, but if the recording was unsuccessful for unexpected reasons, an error processing such as a retry or a replacement processing is performed.
In the case of a DVD-RAM, recorded data reliability is usually increased by actually playing back the medium during the record processing to see if the recorded data has been correctly recorded, and performing a replacement processing using a different recording unit area as required. Management information concerning a re-allocation of a recording area necessitated by the replacement processing is recorded in a special area (defect management area) on the recording medium.
In the known optical recording system as described above, the recorded data in the information recording medium in which the target information is recorded can be basically freely erased and re-written. Accordingly, the target information might possibly be erased and re-written by an erroneous or intentional operation by the user before the target information is displayed. This means that the target information display effect can be lowered.